Electrical connector and method of making it

ABSTRACT

The present invention is an electrical connector in which a substrate (such as a printed circuit board or PCB) includes a plurality of apertures (or vias) and some of those apertures are filled with two materials to improve the characteristics of the electrical interconnection. The preferred process of crating the filled vias includes the steps of plating the vias with an electrically-conductive material to create an electrically-conductive path between portions of the substrate and components associated with the substrate and partially filling the apertures, then filling at least a portion of the apertures or vias with a second or different filling material to seal at least apart of the electrically conductive path through the plating. The second filling material may be chosen to provide thermal compensation for the connection.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to an improved electrical connector andmethod of making it. More specifically, the present invention relates toan electrical connector comprising elastic contacts on an insulatingsubstrate, in which vias or holes in the insulating substrate are filledto provide a better connector performance and improved ease ofmanufacturing.

2. Background Art

Electrical connectors are an important component of many electronicdevices. As the devices become smaller, the functionality is increasing,requiring increasing numbers of electrical interconnections betweencomponents. In order to enable system miniaturization, the electricalconnectors must become smaller, yet they are required to handleincreasing power and signal loads and to operate at faster speeds. It isnecessary in many applications to provide a low-cost, high reliabilityelectrical interconnection on an extremely small scale to allow for anincreasing number of components to be interconnected. As the operatingfrequencies and data transfer rates of the electronic system increases,there is an increased need for high speed signal integrity through theconnector.

Various electrical connectors have been proposed in the prior art.Examples of such electrical connector (electrical interconnection) isshown in Neoconix' prior patents such as U.S. Pat. No. 7,113,408.

Conventional electrical connectors present challenges in terms of theirsize, cost, and operating speed. A conventional connector has asubstantial size and a significant cost to manufacture, especially whenthe connector includes many electrical contacts. Such connectors alsomust operate at speeds which are increasing without losing data as aresult of the electrical connections. Power handling requirements arealso increasing. Conventional connectors are limited in power handlingcapability, and can overheat when power load exceeds their capability.These conventional connectors are typically lacking in their ability todissipate heat or to conduct heat away from the mating components.

Further, many electrical connectors utilize precious metal surfacefinishes, such as gold, to prevent corrosion. These materials arecostly. As a result there is a desire to use smaller connections (totake up less space and to use less precious material), and to minimizethe surface area which must be finished with the precious metals.

Electronic devices and particularly portable electronic devices aresusceptible to corrosion and degradation from liquids or gases from theenvironment that penetrate the system. Electrical connectors typicallyhave a high density of electrical interconnections, and it is difficultto shield these from the environment while maintaining connectorseparability. In contrast, interconnections on a packaged semiconductorcan be over-molded or under-filled to protect the interconnections frommoisture, water, or gas ingress. Hence, the electrical connector tendsto be a highly susceptible component from the perspective of wateringress or damage from corrosive environments.

Accordingly, it will be apparent that the prior art electricalconnectors have limitations and undesirable characteristics.

SUMMARY OF THE INVENTION

The present invention overcomes the limitations and disadvantages of theprior art electrical connectors and methods of making them.

The present invention is an improved electrical connector and method ofmaking it in which the electrical connector may have denseinterconnections, and which provides high reliability interconnections,low resistance and high current carrying capacity, improved thermaldissipation, reduced precious metal usage during fabrication, and thinelectrical conductors while providing improved protection for theelectrical interconnections. This method and connector will allow forsmaller scale interconnections and greater reliability of theinterconnection while providing improved signal integrity at highfrequency and an economical electrical connector to manufacture.

Other objects and advantages of the present invention will be apparentto those skilled in the relevant art in view of the followingdescription of the preferred embodiment and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one form of prior art electrical connector in anenlarged, cut-away or sectional view;

FIG. 2 illustrates one form of an electrical connector of the presentinvention in an enlarged, cut-away or sectional view;

FIG. 3 illustrates a second form of prior art electrical connector in acut-away or sectional view;

FIG. 4 illustrates a second form of an electrical connector of thepresent invention in a cut-away or sectional view;

FIG. 5 illustrates portions of the electrical connector of FIG. 2 or 4as one example of manufacturing progression using the method of thepresent invention;

FIG. 6 is a flow chart illustrating one process for making theelectrical connector of the present invention;

FIG. 7 is a cross-sectional view of an electrical connector whichillustrates other uses for the present invention on multilayer printedcircuit structures containing blind and/or buried interconnections; and

FIGS. 8 a, 8 b, 8 c and 8 d illustrate applications for the use of thepresent invention to create a sealed electrical connector, where FIG. 8c is a front view of a contact pad array on a PCB to which an electricalconnector (or interposer), shown in perspective view of FIG. 8 a, wouldmate, FIG. 8 b is an enlarged perspective view from a different angle ofa portion of the electrical connector (interposer) of FIG. 8 a, showingdetails of its contact array and FIG. 8 d is a cross-sectional viewdepicting one application of that electrical connector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is an enlarged and cross-sectional view of a portion of anelectrical connector 10 of the prior art, such as is described in U.S.Pat. No. 7,113,408 owned by assignee of the present invention, Neoconix.The electrical connector as shown in this view the electrical connector10 has a substrate 12 a plurality of electrical contacts 14 mounted on atop surface 12 a of the substrate 12 and a plurality of contacts 16mounted on a bottom surface 12 b of the substrate 12. The electricalcontacts 14 and 16 are typically formed from an initially flat sheet ofconductive material which has been formed into a three-dimensional shapein a batch process (as described in U.S. Pat. No. 7,758,351, owned bythe assignee of the present invention), with the sheet of electricalcontacts then secured to the substrate 12 in a single operation, thensingulated in a conventional process (such as a chemical etchingprocess).

The substrate 12 is typically non-conducting and made starting with aprinted circuit board (PCB) material such as a sheet of copper-clad FR4.The substrate 12 as shown in this FIG. 1 includes a plurality of throughholes 18 which are formed in a conventional manner. The through holes 18(which are also sometimes referred to as apertures or vias and mayextend completely through the substrate 12 or only partially through thesubstrate 18, terminating at an intermediate layer of the substrate 18)are plated in a conventional manner to provide an electricallyconductive via 18 a through the substrate 12. The copper cladding andplating material also provides conductor portions 12 c, 12 d on the topand bottom surfaces 12 a, 12 b to provide an electrically-conductivepath on these surfaces of the substrate 12 to electrically coupleselected electrical contacts 14, 16. 12 c and 12 d are electricallyconnected to the plated via which provides a conductive path between 12c and 12 d.

The plated through holes are typically formed through a drilling processfollowed by a process to make the hole walls electrically conductive,after which the hole walls are plated through a chemical orelectrochemical process which allows for the wall of the electricallyconductive via 18 a to be of a controlled thickness to providesufficient conductivity and reliability. The standard through hole orvia 18 with plating 18 a of the prior art electrical connectors is thusnot filled completely, but only around the periphery of the cylindricalopening, having a hollow or open center portion, represented by thereference numeral 18 c.

FIG. 2 illustrates an electrical connector 10′ of the present inventionwhich is a modified version of the connector 10 of FIG. 1. In this view,the connector 10′ includes a substrate 12 with a plurality of throughholes 18 and a plurality of electrical contacts 14 mounted to the topsurface 12 a of the substrate 12 and a plurality of electrical contacts16 mounted to the lower or bottom surface 12 b of the substrate 12. Afirst conductive material (a plating material) is shown applied to theaperture to provide the plating layer 18 a as an electrical connectionwith selected electrical contacts 14, leaving a cylinder-shaped openingwithin the aperture 18. A fill material 18 b substantially fills thecylinder-shaped void, providing a covering and sealing material over atleast a portion of the plating material 18 a within the aperture 18.

The preferred fill material 18 b for many applications of the presentinvention is thermosetting epoxy, a plastic material. However, othermaterials can be used to advantage in the present invention includingother thermo-setting materials (such as acrylic, polyimide, or Bakelite)or thermoplastic material (such as PMMA, thermoplastic polyimide, orLCP). Other materials which could be used to advantage as the fillmaterial 18 b in the present invention include solder mask,fluoropolymers, and other polymers and blends of polymers. The via fillmaterial 18 b also can be a composite polymeric material includingparticulate or fiber filler materials such as glass fibers, alumina,silicon carbide, magnesium oxide, or silicon dioxide (silica) particlesto control thermal expansion or to increase thermal conductivity, wheresilica is particularly useful in mixtures to achieve a desiredcoefficient of thermal expansion. The via fill material also can includeconductive fillers such as silver flake or metal particles includinggold, copper and/or silver to improve conductivity and/or reliability.In yet some other applications, a via fill material can be anelectrically conductive material—a metal such as copper or an alloy suchas solder. The filler could include copper which has been platedsufficiently to completely fill the via. The solder filler could becreated by printing solder paste into the vias, then reflowing to createa solder via fill.

The via fill material 18 b can provide a mechanical strengthening of theelectrical connection provided by the plated via. This via fill materialreduces the stress on the via plating layer 18 a during electricalconnector operation, including reducing stress during thermal cycling orduring activation of the electrical connector (for example, from flexingof the electrical connection structure or from expansion and contractionof the substrate 12). The present invention also contemplates that thevia fill material might provide a sealed connector in some applications,including with a separate seal such as an o-ring, If desired. A sealedconnector provided by (or in conjunction with) the via fill material canprotect the sensitive electronic components inside of an electronicdevice from gases and liquids which might erode or corrode theelectronic components and reduce the effectiveness and the useful lifeof the electronic system.

The via fill material 18 b may be chosen based on the application underconsideration. In some cases, it is desirable to have a coefficient ofthermal expansion which is selected based on the coefficient of theplating material (approximately equal to that of the plating material).In other applications, it is desirable to have a coefficient of thermalexpansion which is approximately the same as the coefficient of thermalexpansion of the substrate. In still others, it is desirable to have acoefficient of thermal expansion which is approximately the average ofthe coefficients of thermal expansion of the plating material and thesubstrate.

The via fill material 18 b might be thermally conductive in otherapplications. This can be accomplished by using thermally conductivefillers in the via fill material, such as metals (for example copper)and certain ceramic materials (for example boron nitride, aluminumnitride, or aluminum oxide). Using a thermally conductive fill materialwould improve the heat transfer through the electrical connector 10′ andreduce the heat retained at the electrical interconnections ortransferred to the mating components, which may be heat sensitive. Thiscan effectively increase the current carrying capacity of the connector,and as a result may reduce the number of high power interconnectionsrequired and/or improve the reliability of the system.

The via fill material 18 b might be electrically conductive in certainother applications. This can be accomplished by including a metal (suchas copper, silver, or gold) or a metallic alloy (such as solder) withinthe fill material. This type of material can reduce the electricalresistance through the electrical connector 10′, enabling high currentcarrying capability. This increased current carrying capacity can reducethe number of connector contacts (“pins” or “positions”) required toprovide sufficient power to a device or system element. This can alsoreduce the heat generation due to resistive heating and can also improvesignal integrity.

Because the elastic contacts commonly require surface finishing with aprecious metal such as gold, to ensure low contact resistance andprevent corrosion, and the surface finishing frequently occurssubsequent to attachment of the contacts to the substrate, the via orplated through hole will typically incidentally be plated with theprecious metal, increasing gold usage. The via fill material preventsthe walls of the via from being plated with the precious metal, hencereducing precious metal usage and therefore fabrication cost.

In a connector structure where all of the vias are filled, the connectorstructure may be sealed from side to side and prevents moisture or wateringress through the connector structure. By sealing the perimeter of theconnector to another component or element of the electronic system, awatertight connector can be achieved. This is a significant advantage,for example, for battery connectors for cell phones, where the batteryside of the connector may have significantly higher likelihood ofexposure to water than the electronic components within the main body ofthe phone housing. The sealed connector would prevent water ingress fromthe battery side of the connector into the main body of the phone, wheresensitive electronic devices inside including semiconductor devices suchas processor chips, memory chips, and logic chips reside.

The present invention is related to electrical connectors in general andis not limited to electrical connectors having a plurality of springcontacts on the top and bottom of the electrical connector, and it isnot limited to a connector having electrical contacts on both top andbottom portions of the connector. So, in place of one set of theelectrical contacts, an array of surface mount pads could be employed.In the alternative, the contacts could be a ball grid array (BGA), ifdesired, FIG. 3 illustrates the use of a ball grid array (BGA) contacts19 in the electrical connector 10 of the prior art. The electricalconnector 10 includes the substrate 12 with its top surface 12 a and itsbottom surface 12 b, with a plurality of spring electrical contacts 14on the top surface 12 a. The substrate 12 includes a plurality ofthrough holes or vias 18 with plating 18 a on the vias or through holes,leaving a void or open space 18 c within the vias 18. A grid array ofballs 19 is mounted to the bottom surface 12 b in a conventional mannerof soldering the balls in place. However, since the solder would wickinto the apertures if the balls were located over a via 18 with its openvoid 18 c or in close proximity thereto, these balls 19 must be spacedfrom the open vias 18 of this electrical connector 10.

FIG. 4 illustrates the electrical connector 10′ of the present inventionwith such an array of electrically conductive balls 19 mounted to thelower surface 12 b of the substrate 12. The apertures or vias 18 throughthe substrate 12 have been plated with a plating material 18 a and therest of the aperture has been filled with the fill material 18 b. Thefill material 18 b prevents the solder from wicking into the hole,allowing the placement of a solder ball 19 over an aperture or in closeproximity thereto.

FIG. 5 illustrates the substrate of the electrical connector of thepresent invention as it progresses through one typical manufacturingprocess, up to but not including the attachment of the sheet of elasticcontacts to the substrate. Many variations on this manufacturing processcan be made and additional steps can be inserted if desired forparticular applications. In step 1, a copper clad FR4 printed circuitboard substrate 12 e is shown as the starting material, with layers 12 fof copper on top and bottom of the insulating material 12 g. In step 2,a substrate 12 h is shown after the apertures or vias 18 (sometimescalled through holes) have been formed, preferably using a drillingprocess. At step 3 a substrate 12 i is shown after the seeding andplating process has formed plated paths 18 a through at least some ofthe vias 18, but leaving the open region or void 18 c within theaperture 18 adjacent to the plating 18 a. At step 4, a substrate 12 j isshown with fill material 18 b inserted into the void 18 c of step 3. Atstep 5, the fill material 18 b is cured and shrinks and the surfaces(top and bottom, as desired) may be cleaned mechanically or chemicallyto remove residual material such as resin from the surface of the fillmaterial 18 b. At step 6, the substrate 12 m now has undergone circuitformation through the use of a “print and etch” process. Portions of theconductive material at 12 n have been removed to provide the circuit inthe desired interconnection in a well known manner.

Of course, it will be understood that many variations to this processare possible without departing from the spirit of the present invention.So, for example, if the fill material 18 b does not substantially shrinkduring the cure process, planarization may be necessary (e.g., bymechanical abrasion) so that the hole fill 18 b surfaces have thedesired relationship to the surface of the substrate. If the fillmaterial shrinks too much, then an additional fill step might be desiredto bring the level of the fill material to the desired level. If it isdesired to have the fill material 18 b recessed from the surface of thesubstrate—for example, to prevent interference with the movement of thespring contacts), the surface of the substrate can be plated with copperin selected locations.

FIG. 6 illustrates the steps of one preferred process for making theelectrical connector of the present invention. The process begins withthe substrate 12 at step 100, with the preferred substrate being printedcircuit board with copper cladding. At step 110 the apertures or vias 18are formed, preferably using a drilling process. This drilling processcould include mechanical drilling, laser drilling, plasma drilling, orother means of hole making. Next at step 120, the apertures 18 areseeded and plated using conventional methods, forming vias 18 with aconductive coat 18 a and a cylinder-shaped openings 18 c. Thecylinder-shaped openings 18 c in the vias 18 are filled using a secondmaterial at the step 130. This fill process can be accomplished byseveral means, including screen printing, stencil printing, anddispensing. Screen printing can be done from one side or from both sidesof the substrate and with or without vacuum assist to help pull the fillmaterial into the vias. In many applications it is preferred to use asingle-sided screen printing using vacuum assist to ensure completefilling of the apertures 18 (where the plating does not fill the via oraperture). Of course, there are other ways to insert the fill materialwithin the voids, including dispensing it and stencil printing it. Afterthe fill material is positioned within the aperture, the preferredmethod of filling the voids involves heating the fill material to cureit, if it is a thermoset polymer or filled thermoset polymer, or toreflow it if it is a solder paste or thermoplastic polymer, topermanently fill the voids. It is also possible to cure the fillmaterial with ultraviolet (UV) radiation, if a UV curable polymer isused as the fill material. The cure processes stabilizes and solidifiesthe fill material. The surface of the processed substrate 12 is thencleaned at step 140, preferably using a plasma cleaning process,although a chemical or mechanical cleaning are also possible. Now, thefill material may be in an acceptable position as a result of thisprocessing or it may require planarization. If the fill materialprotrudes above the surface of the plated, copper clad substrate, aplanarization operation will likely be required, such as abrasivesanding, brushing, plasma etching, or polishing, to flatten the fillmaterial so it is coplanar with or slightly recessed from the surface ofthe copper. If the fill material shrinks substantially during curing, itmay be recessed from the surface of the plated, copper clad substrate.It is possible a second via filling process may be required to fullyfill the via. At the step 150 printing and etching is done to provide asurface with the appropriate conductive attachments. Alternatively, apattern plating process or semi-additive circuit formation process canbe used to provide the appropriate conductive attachments. Then at step160 the elastic contacts are attached to the conductive attachments,preferably by positioning the sheet of elastic contacts in the properlocation, bonding and interconnecting the sheet of electrical contacts,then singulating the contacts.

Finally, if some further finishing of the surface of the fill materialis required or desired, it may be done, such as adding a metallizationlayer on top of the fill material (which can be accomplished throughplating or other suitable methods).

FIG. 7 illustrates a variation on the present invention wherein theelectrical connector includes a multilayer printed circuit board (PCB).This electrical connector 10″ includes a PCB or substrate 12″ havingmultiple conductive lawyers separated by insulating layers made in aconventional, known manner. The substrate 12″ has its top surface 12 aand its bottom surface 12 b each having electrical contacts 14, 16mounted thereon. As shown in this view, there is a blind via 50 and aburied via 60 illustrated in this view, where the blind via 50 isbeneath a connection plate and the buried via is between two internalconductive layer s 60 c, 60 d of the substrate 12″. The filling of theblind via 50 includes a conductive material 50 a and a second material50 b which fills the rest of the hole (the void). The filling of theburied via 60 includes a conductive material 60 a and a second material60 b filling the void of this via. While the filling of the blind viason the outer layers of the substrate provides the advantages listedabove, the filling of the buried via is optional and depends on thecircuit layout and the nature of the multilayer printed circuit boardfabrication process.

FIG. 8 a is a perspective view of an electrical connector (orinterposer) 240 which provides interconnections including board-to-boardor flex-to-board electrical interconnections. A plurality of electricalspring contacts 250 are arranged in an array on the electrical connector(interposer) 240, where the electrical spring contacts 250 arepreferably the spring contacts of the type sold by Neoconix under itsPCBeam trademark and described in its issued patents. A seal 260surrounds the array of electrical contacts 250, with the seal 260 beinga conventional o-ring or other suitable seal. The seal 260 could also becomprised of the coverlay material 270, where the coverlay in thisinstance would be substantially compliant, such as an elastomericmaterial like silicone. When the electrical connector (interposer) 240is mated to and compressed against the substrate, the seal 260 forms awatertight barrier to fluid penetration. Not shown in this view are thefilled vias, which also contribute to forming the watertight connectorby preventing water ingress or egress through the vias.

FIG. 8 b shows the detail of a portion of the electrical connector(interposer) 240 with some of the electrical spring contacts 250 whichare mounted such that their base portion is located under a coverlay270. Spring contacts 250 are located in openings 280 in the coverlay270. Not shown in this view are the filled vias of the present inventionwhich cooperate with the other structures to assist in prevention ofmoisture or water penetration while protecting the electricalinterconnections provided by plating of the vias.

FIG. 8 c shows a mating substrate 200 having a 6×5 array of contact pads210 arranged on a PCB or flex circuit substrate 215. An optional copperseal ring 220 surrounds the contact pads 210. The contact pads 210 areelectrically connected by internal vias to electronic circuits on and/orwithin the substrate. The copper seal ring 220 helps provide a seal byproviding a raised surface which compresses against compliant seal onthe electrical connector 240 of FIGS. 8 a and 8 b, such as an o-ring orother compliant member, during actuation of the connector to thesubstrate 215. The seal formed between the substrate and the connectoroutside of the contact array, in conjunction with filled vias in theconnector interposer, restricts the passage of fluids, such as water ormoisture, protecting the electrical connections.

FIG. 8 d shows one representative example of the electrical connector(or interposer) 240 to form a watertight electrical interconnection tothe inside of a sealed electronic system 290 surrounded by a housing,360. A seal 260 surrounds the contact array and is compressed betweenthe electrical connector (or interposer) 240 and the mating printedcircuit substrate 200, and/or the housing. The filled vias 310 preventwater ingress through the connector (interposer) 240, and electricallyinterconnect electrical contacts 250 on a first surface 340 of theelectrical connector (or interposer) 240 to electrical contacts 320 on asecond surface 350 of the connector (or interposer) 240. An electricalinterconnection is made between the electrical contacts 250 on the firstsurface 340 of the connector (interposer) 240 and mating pads (notshown) on the printed circuit substrate 200. On the second surface 350of the connector (interposer) 240, electrical interconnections are madebetween the electrical contacts 320 and a device 300, such as a battery,power supply, or antenna, located outside of the sealed electronicsystem 290, and thus potentially exposed to the outside environment 330.

Many modifications and alterations of the preferred embodiment describedabove are possible without departing from the spirit of the presentinvention. For example, the filled via can be created using a plating oretching process to create a copper or other metal post or pillar on thesurface of a carrier sheet, and this post can be inserted into a hole inthe non-conductive substrate material to create the solid or filled via.Further, some of the features of the present invention can be used toadvantage without the corresponding use of other features. For example,the use of an abrasion of the fill of the vias may be desirable in someinstances and not required in other instances. Accordingly, theforegoing description of the preferred embodiment should be consideredas merely illustrative of the principles of the present invention andnot in limitation thereof, as the claims which follow are the soledefinitions of the present invention.

1.-23. (canceled)
 24. An electrical connector comprising: a substratehaving a first surface and a second surface and carrying electricalcontacts on at least one surface and a plurality of apertures extendingbetween the first surface and the second surface, said electricalcontacts including an elastic portion; an electrically-conductivematerial which extends through at least one of the plurality ofapertures and electrically couples the first surface and the secondsurface; and an additional material in addition to the conductivematerial which is included within at least one of the plurality ofapertures, said additional material sealing at least a portion of theelectrically-conductive material from exposure to the environmentoutside the substrate, said additional material chosen to have acoefficient of thermal expansion approximating the coefficient ofthermal expansion of at least one of the substrate and theelectrically-conductive material.
 25. An electrical connector of thetype described in claim 24 wherein the additional material is chosen tohave a coefficient of thermal expansion between the coefficient ofthermal expansion of the substrate and the coefficient of theelectrically conductive material.
 26. An electrical connector of thetype described in claim 24 wherein the additional material includes athermosetting epoxy material.
 27. An electrical connector of the typedescribed in claim 24 wherein the additional material is filled withsilica particles.
 28. An electrical connector of the type described inclaim 24 wherein the additional material is filled with a material withhigh thermal conductivity.
 29. An electrical connector of the typedescribed in claim 24 wherein the additional material includes a fusiblemetal.
 30. A method of making an electrical connector comprising thesteps of: providing a connector substrate with a plurality of apertures;defining a plurality of electrically-conductive contacts on a flat sheetof conductive material, forming the flat sheet into a three-dimensionalform with a plurality of elastic electrical contacts, attaching thethree-dimensional conductive sheet with a plurality of electricalcontacts to the substrate and singulating the electrical contacts;providing an electrically-conductive path through at least one of theapertures and attaching at least one of the electrical contacts to theelectrically-conductive path through the substrate; choosing anadditional material which has a coefficient of thermal expansionapproximating the coefficient of thermal expansion of at least one ofthe substrate, the electrical contact and the electrically-conductivepath; and inserting the chosen additional material into the aperture toprotect the electrically-conductive path by providing a sealing of atleast part of the electrically-conductive path.
 31. A method includingthe steps of claim 30 wherein the step of filling includes the step ofchoosing a fill material with a characteristic based on at least onecharacteristic of the substrate.
 32. A method including the steps ofclaim 30 wherein the step of filling includes the step of choosing afill material with a characteristic based on at least one characteristicof the electrically conductive path.
 33. A method including the steps ofclaim 30 wherein the step of filling includes the step of choosing afill material with a characteristic based on at least one characteristicof at least one of the substrate, the electrical contact and theelectrically conductive path through the substrate.
 34. A methodincluding the steps of claim 30 wherein the step of choosing a fillmaterial includes the step of choosing a material with a suitable amountof silica included therein to provide the desired coefficient of thermalexpansion.
 35. An electrical connector comprising: a substrate includingan insulating body, at least one mounting surface and a plurality ofapertures extending at least partially through the substrate; a set ofelectrical contacts carried on the mounting surface of the substrate andat least some of the electrical contacts being proximate at least someof the apertures, the electrical contacts including at least one elasticspring contact; a first conductive material within at least some of theapertures and in contact with at least one of the electrical contactsproviding an electrical path coupling the one electrical contact with asecond surface of the substrate, said first conductive material onlypartially filling the apertures into which the first conductive materialis within; and a second material in the same aperture in which the firstconductive material has been inserted, said second material covering atleast part of the first conductive material and filling at least part ofthe aperture, said second material having a coefficient of thermalexpansion which approximates the coefficient of thermal expansion of atleast one of the substrate and the first conductive material.
 36. Anelectrical connector of the type described in claim 35 wherein thesubstrate has a second mounting surface comprising mounting pads for atleast one chosen from solderballs and surface mount attachments, whereat least one of the mounting pads is electrically connected to at leastone of the electrical contacts.
 37. An electrical connector of the typedescribed in claim 35 wherein the second material comprises athermosetting epoxy.
 38. An electrical connector of the type describedin claim 35 wherein the second material has a coefficient of thermalexpansion which has been chosen based on the coefficient of thermalexpansion of the first material.
 39. An electrical connector comprising:a substrate having a first surface and a second surface and carryingelectrical contacts on both surfaces and a plurality of aperturesextending between the first surface and the second surface, saidelectrical contacts including an elastic portion; anelectrically-conductive material which extends through at least one ofthe plurality of apertures and electrically couples the first surfaceand the second surface; and an additional material in addition to theconductive material which is included within each of the plurality ofapertures, said additional material sealing the apertures to preventingress of fluid materials through the apertures; a sealing mechanismaround the perimeter of at least the connector first surface, saidsealing mechanism comprising a compliant material, said sealingmechanism providing a fluid ingress-inhibiting seal around the perimeterof the connector area containing the electrical contacts when compressedagainst a mating surface of an electrical component, such as a printedcircuit board.
 40. An electrical connector of the type described inclaim 39 wherein the sealing mechanism comprises an O-ring.
 41. Anelectrical connector of the type described in claim 39 wherein thesealing mechanism results from the use of a compliant coverlay materialon the connector surface.
 42. An electrical connector of the typedescribed in claim 41 wherein the compliant coverlay material iscomprised of an elastomer.
 43. An electrical connector of the typedescribed in claim 41 wherein the compliant coverlay material iscomprised of a closed cell foam.
 44. An electrical connector of the typedescribed in claim 41 wherein the compliant coverlay material iscomprised of an open cell foam which deters ingress of liquid whensufficiently compressed.
 45. An electrical connector of the typedescribed in claim 39 wherein a sealing mechanism is included on bothsurfaces of the connector.
 46. An electrical connector comprising: asubstrate including an insulating body, at least one mounting surfaceand a plurality of apertures extending at least partially through thesubstrate; a set of electrical contacts carried on the mounting surfaceof the substrate and at least some of the electrical contacts beingadjacent to or on top of at least some of the apertures, the electricalcontacts including at least one elastic spring contact; a firstconductive material within at least some of the apertures and in contactwith at least one of the electrical contacts providing an electricalpath coupling the one electrical contact with a second surface of thesubstrate, said first conductive material only partially filling theapertures into which the first conductive material is within; and asecond material in the same aperture in which the first conductivematerial has been inserted, said second material covering completelyfilling the apertures; and a sealing mechanism around at least theperimeter of at least the connector first surface, said sealingmechanism comprising a compliant material, said sealing mechanismproviding a seal which inhibits the ingress of liquids from around theperimeter of the connector area containing the electrical contacts whencompressed against a mating surface of an electrical component, such asa printed circuit board.